Linear bearings find widespread use throughout industry and are vital components in every machine which requires that one part move relatively to another part smoothly, precisely and accurately along a linear track. Linear bearings are found in machine tools such as milling machines, in processing equipment, optical devices and agricultural equipment, to name only a few examples.
Linear bearings have an elongated support, such as a rail on which a carriage is mounted for lengthwise sliding movement. The support serves as a guide way for precisely and accurately positioning the carriage at a desired location or moving the carriage over a precise path at a predetermined speed. The carriage carries a component, such as a milling head with a cutting tool, and the use of the linear bearing allows the cutting tool to be brought to bear on a workpiece for the precise and accurate machining of a metal part. Ball or roller bearings may be used between the support and the carriage to facilitate the sliding motion of the carriage along the support. The interface between the carriage and the support may be lubricated to eliminate friction and ensure smooth sliding motion of the relatively moving parts. Dimensional tolerances required between the support and carriage will vary depending upon the application. For example, linear bearings used in machine tools or as optical benches will require very close tolerances allowing for precise control of motion and positioning of the carriage, whereas greater dimensional variations may be acceptable for processing or agricultural equipment. The size of the linear bearing will vary with the application as well, from heavy, robust bearings used in machine tools to lightweight bearings for use in a laboratory.
It is often necessary to protect linear bearings from their immediate environment to ensure their continued smooth, precise and accurate operation. This is especially critical for linear bearings used in machine tools which are constantly subjected to foreign particles such as dirt, dust, metal filings and chips or other debris typically present in a machine shop. The lubricant on the support causes the foreign particles to adhere to its surface and even the smaller foreign particles can adversely affect the bearing's operation due to the close tolerances between the support and the carriage. Particles which accumulate on the support hinder the smooth motion of the carriage, causing it to jam or stick, to move erratically, to lose positioning accuracy and increase the wear between the relatively moving parts, thus, reducing the life of the bearing.
It is known to sheath the support with a flexible protective cover, in the form of a bellows, to prevent foreign particles from accumulating on it. One end of the bellows is attached to an end of the support, and the other end of the bellows is attached to an end of the carriage proximal to the support end. The folds of the bellows are oriented perpendicularly to the long axis of the support and thus allow the bellows to expand or compress as needed along the length of the support to compensate for the motion of the carriage relative to the support end and keep the support covered. There is usually a separate bellows on each side of the carriage ensuring coverage of the entire support.
Bellows are subject to constant flexing as the carriage moves along the support and thus wear out over time. Replacement of the bellows is a time consuming process because the bellows are typically fastened to the support end and carriage end with bolts which must first be removed (using tools such as a wrench or nut driver) to free the bellows, and then the new bellows must be positioned over the support and bolted in place (again using tools). While it is a simple procedure, it takes time to effect the changeover and the machine tool or other apparatus is idle during this servicing.
Machine downtime adversely affects production efficiency and consequently profits, and it is desirable that downtime be minimized whenever possible. This is especially true when one considers the cumulative effect on production efficiency when the downtime is summed over many machines. There is a clear need for an apparatus and a method which will allow the bellows on linear bearings to be changed simply and rapidly, without the need for tools, thus, minimizing machine downtime and increasing production efficiency.